The invention relates to a connection for transmitting torque between an internally toothed hub and an externally toothed shaft insertable into the hub. The internal hub teeth and the shaft teeth are provided with different tooth flank profiles such that the tooth flanks of the shaft teeth rest against the tooth flanks of the internal teeth on a pitch circle diameter D.sub.T. Thus, off the pitch circle diameter, a clearance between the tooth flanks exists in the circumferential direction.
When torque is transmitted by such connections, a torsional or shear stress occurs in the shaft. The stress reaches its maximum in the transition cross-section of the shaft at the hub end positioned towards the shaft shank. In the course of further axial extension of the shaft, stress is reduced within the hub. In conventional designs, the transition cross-section constitutes a critical area where the tooth profiles may be damaged or the shaft may be sheared off.
U.S. Pat. No. 4,115,022 describes a connection between a hub and a plugged-in shaft. Here the internal teeth of the hub and the shaft teeth are each provided with straight flanks and thus with similar profiles. The tooth form on the shaft teeth is such that the tooth thickness changes axially. The maximum tooth thickness occurs in the axially central region of the tooth, with the minimum tooth thickness occurring at the free shaft end and in the transition cross-section of the shaft shank at the hub end. The tooth form allows shaft torsion beyond the transition cross-section within the hub, thereby ensuring that the torsional load on the shaft is improved and more uniform and that the tooth flanks are subjected to a uniform load. In consequence, the risk of the tooth profiles being damaged and the shaft being sheared off in the transition cross-section is reduced.
However, such a shaft tooth profile whose thickness changes along the shaft axis requires an expensive machining operation. Furthermore, a shaft profile with straight tooth flanks is produced less advantageously than a shaft profile obtained as a result of rolling processes of tool and workpiece. Moreover, half of the axial length of the shaft teeth profile positioned towards the free end of the shaft remains load-free and unused.